Valve actuating mechanism



Dec. 31, 1940.

Filed May 9, 1939 Patented Dec. 31, 1940 A UNITED STATES PATENT OFFICE VALVE ACTUA'I'ING MECHANISM Louis E. Spencer, West Hartford, Conn.

Application May 9, 1939, SerialNo. 272,656

2 Claims.

"This invention relates to improvements in valve actuating mechanisms of the type wherein a rocker arm engages the valve stem for effecting reciprocatory motion of the latter.

The rocker arm itself is generally actuated by means which rock the arm in one direction to move the valve stem in one direction, while the stem and arm are returned in the opposite direction usually by a spring. During this return motion, difliculties have been encountered in some structures in maintaining a fiat contact between the surface of the rocker arm and the surface of the rocker arm actuator and the primary object of the present invention is to provide a valve actuating mechanism wherein it is insured that the surface of the rocker arm will lie flat against the surface of its actuating member at all times.

A further object of the invention is to provide a rocker arm for a valve actuating mecha-- nism which is capable of rotating in a plane transversely of the plane in which the rocker arm is rocked.

A still further object of the invention is to provide a valve actuating mechanism wherein the rocker arm is permitted a limited longitudinal movement.

More specifically, the invention contemplates a valve actuating mechanism wherein the rocker arm is journaled in a member which is rotatable in a plane transversely of the plane in which the rocker arm rocks, said member, together with the arm, possessing a limited movement axially of said member or longitudinally of the arm, and the rotary motion of said member being limited to the desired de ree.

With these and other objects in view, the invention consists in certain details of construction and combinations and arrangements of parts, all as will hereinafter be more fully described, and the novel features thereof particularly pointed out in the appended claims.

In the accompanying drawing- Figure 1 is a sectional, elevational view, longitudinally of the rocker arm, the latter being shown in full;

Fig. 2 is a horizontal, sectional view on the line 2-2 of Fig. 1;

Fig. 3 is a vertical, sectional View on the line 3-3 of Fig. 1; and

Fig. 4 is an end elevation illustrating, in full lines, the normal engagement between the rocker arm and its actuator and, in dotted lines, the abnormal engagement of said elements that would be possible in the absence of the invention.

In the construction illustrated, the rocker arm 10 isadaptedto be rocked by a cam H mounted on cam shaft I2, the downward motion of the 5 valve stem I3 caused by the depression of the rocker arm compressing springs M which will return or elevate the stem and rocker arm as the cam I I continues to revolve and the lower portions of the cam surface come into engagement with said rocker arm. Usually, the upper surface of the rocker arm which engages against I the-surface of the cam II is curved longitudinally, as illustrated and, heretofore, difiiculties have been encountered by reason of the accuracy with which the surface of the actuator, the cam II in the present instance, and the surface of the rocker arm has to be assembled. In other words, it requires a high degree of accuracy in assembling the rocker arm and its actuator to cause the curved surface of the rocker arm to lie or engage fiat against the surface of its actuator or cam II. In the event the rocker arm does not lie flat against the surface of the cam, particularly during the upward movement of the rocker arm, the metal at the contact point will be overstressed and start breaking away. This so-called abnormal engagement of the rocker arm and cam surface can be more readily appreciated by an inspection of Fig. 4, wherein the rocker arm is'illustrated, in dotted lines, as being slightly tilted, under which circumstances it will be seen that it makes a point contact with the cam surface II, as distinguished from a line contact. Naturally, where there is such a point contact, stresses are localized and, consequently, the tendency of the metal to break away.

In accordance with the present invention, these difiiculties are eliminated by permitting the rocker arm to rotate substantially on its longi- 40 tudinal center or in a plane transversely of the plane in which it is adapted to be rocked by its actuating cam. For instance, the rocker arm may be journaled to rotate in bearings l5 formed in a circular member I6 which, likewise, is journaled. for rotary motion in the wall H of the mo tor casing or block, the rotary motion permitted the circular member l6 being in a plane transversely of the rocker arm or the plane in which the rocker arm is adapted to rock in its bearings 5 15. In the present instance, the rocker arm is provided with trunnions I8 journaled in the bearings I5, but it will be appreciated that these trunnions are no more, in effect, than a shaft on which the rocker arm might either be fixed present or pivotally supported. The essential point is that the member I6 shall be capable of rotating in the recess in which it is seated in the engine block, and that the plane in which said member rotates shall be ldisposed transversely of the plane in which the rocker arm rocks.

Only' a limited rotary motion of the circular member [6 is required to permit or insure proper engagement of the rocker arm with the rocker cam. For limiting the rotary motion of said member, the surface thereof is formed with an axially disposed 'slot [9 and, extending through the engine block into said slot, there is a pin 2|], the width of said pin transversely of said slot being slightly less than the width of the slot itself, as illustrated in Fig. 3. Thus, the rotary motion of member [6 is limited to the clearance that is provided between the pin 20 and the side walls of recess l9. With this arrangement, any slight error in the assembly of the rocker arm and its actuating cam can be easily corrected, or will be compensated for, by the member I6 automatically adjusting "itself circumferentially to accommodate the surface of the rocker arm against the surface of the cam in a fiatwise rela tionship.

Thecam II is rotated in the direction of the arrow 2|, in Fig. 1, and, as a consequence, there is a longitudinal pull imposed on the rocker arm in the direction of the arrow 22, so that there is a tendency to force the member I6 against the inner surface of the recess in which it is seated, but to insure maintenance of the member IS in this position, means are provided for imposing an endwise thrust directly on said member. For instance, one or more springs 23 may be interposed between said member IB and the cover plate 24 for the recess in which said member is seated. Thus, the springs constantly urge the member I6 and the rocker arm toward the cam and valve stem, the movement of said members in that direction being, of course, limited by the inner wall of the recess. In this way, the rocker arm maintains a constant relationship with respect to its actuating cam and the valve stem, notwithstanding the fact that it is carried on what might be termed a floating member. In other words, although the circular member I6 is, in a sense, free in its recess, the longitudinal disposition of the rocker arm is constant.

What I claim is:

1. In a Valve actuating mechanism, a cylindrical rotatable member closed at one end, means engageable with said end yieldingly urging said member axially-in the direction of its opposite end, a rocker arm pivoted in said member and projecting from said opposite end, and a stop engageable with said member for limiting the rotary motion thereof. 7 I

2. In a valve actuating mechanism, a cylindrical rotatable member, a rocker arm pivotally supported in said member and projecting from .one end thereof, means for limiting rotary motion of said member, and means yieldingly urging said member axially in the direction in which the rocker arm projects from said member.

LOUIS R. SPENCER. 

